1. Field of the Invention
The present invention relates to a method and system for controlling a vehicle transmission for realizing smoothing of acceleration and deceleration and efficiently using the power source energy, thereby realizing desired feeling of acceleration and deceleration.
2. Description of the Prior Art
The conventional speed ratio control method of a transmission is described in International Congress On Transportation Electronics Processings (1988), pp 33 to 42 (hereinafter referred to as Prior Art 1). In the present invention, the target speed ratio is determined from the real speed ratio, engine throttle opening, and vehicle velocity, and the speed ratio variation velocity is determined from the following expression: ##EQU1## and the speed ratio is controlled so that the real speed ratio variation velocity matches this speed ratio variation velocity. The factor 1 of the above expression is changed by fuzzy logic rules depending on the vehicle velocity and engine throttle opening. The factor 2 is changed by fuzzy logic rules depending on the "target speed ratio--real speed ratio" and target speed ratio variation velocity. Changing the speed ratio characteristics of a continuously variable transmission is described in Japanese Patent Application Laid-Open No. 1988-269744 (hereinafter referred to as Prior Art 2).
In the above Prior Art 1, the user can set desirable speed ratio characteristics by inputting of the relational curve between vehicle velocity and engine speed, and selecting one of "fast", "medium", and "slow" of the speed ratio variation velocity.
In the above Prior Arts 1 and 2, synchronization between the time that the deviation becomes 0 and the time that the speed ratio control actuator stops speed ratio change, use of vehicle acceleration information, and engine control are not considered, and there are problems imposed such as unsmooth changes of acceleration and overshoot of engine speed. The easiness of maneuverability is not considered, and there is a problem imposed such that when the throttle opening is changed, the speed ratio is changed always and the engine speed changes widely.